Heat exchange device with convoluted heat transfer wall

ABSTRACT

A heat exchanger device with a convoluted heat transfer wall to define a first and second set of flow channel defining pockets having oppositely opening mouths. Each set of pocket mouths communicates with a separate fluid inlet and fluid outlet means disposed adjacent opposite ends of the pocket mouths. Sets of continuous ridges fit into the pocket mouths between each fluid inlet and outlet to provide flow channels of unvarying width by preventing transverse movement of the convolutions of the heat transfer wall, as well as to seal the pocket mouths between each fluid inlet and outlet.

United States Patent Leonard etal.

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I 1 1. {f i PATENTEDIEB 8:912 3 640 340 SHEET 2 UF 2 HEAT EXCHANGEDEVICE WlTH CONVOLUTED HEAT TRANSFER WALL BACKGROUND OF THE INVENTIONThe growing art of organ perfusion requires compact apparatus for heatexchange between separate fluids, and particularly for heat exchangebetween blood and a heat transfer fluid. The same heat exchangeequipment is also useful for warming or cooling the blood of a patientduring surgical operations and the like.

ln Transactions-American Society for Artificial Internal Organs, Vol. 6,pp. 360-369, Esmond et al. discloses a disposable stainless steel bloodheat exchanger which uses a convoluted heat transfer wall for definingtwo separate sets of oppositely opening pockets. Each set of pocketsforms a multiple path flow conduit for a separate fluid whichinterleaves with the other multiple path flow conduit, providingabundant surface area for heat exchange in a very small space.

However, certain disadvantages arise with the convoluted heat exchangedevices of the prior art. In particular, the individual convolutions ofsuch a convoluted heat transfer wall are quite flexible and springy, andthey are easily moved laterally back and forth in the manner of anaccordion bellows. The result of this is that the flow channels withinthe pockets defined by the convolutions may easily vary in thickness,especially when there is a difference in the pressure of the two fluidsin the separate flow channels. Hence it is difficult in the prior artdevices to keep the flow channels at a desired optimum thickness for thebest heat transfer and flow efficiency because of the high flexibilityof the convoluted heat transfer wall. Even if support studs areintermittently provided in the pockets in the manner of U.S. Pat. No.2,953,l l0, a substantial variation in the thickness of the various flowpaths can still take place through accordionlike flexing, as well asthrough bowing of the walls between the studs when a differentialpressure is present in the two flow paths. Differential pressures of upto about p.s.i. are typically used in the devices for heat exchangebetween blood and another fluid.

Furthermore, in the prior art devices, the blood is free to migrate outof the mouths of the pockets in substantial quantity, passing intolow-flow areas adjacent the pocket mouths, where it can stagnate andclot. The presence of such a large amount of clotting blood can resultin the relatively rapid spread of blood clotting, and pieces of clottedblood passing downstream along with the fresh blood.

DESCRIPTION OF THE INVENTION The heat exchange device of this inventionutilizes a convoluted heat transfer wall to define first and second setsof oppositely opening pockets, with a separate fluid inlet and fluidoutlet disposed adjacent opposite ends of each set of pocket mouths.Sets of continuous sealing ridges are disposed to fit into each pocketmouth between each fluid inlet and outlet. This greatly reducestransverse movement of the convolutions of the heat transfer wall,providing flow channels of unvarying width, even in the presence of therelatively high differential pressures of 10 p.s.i. or more betweenfluids flowing in the separate sets of pockets. Furthermore, the sealingridges greatly reduce the migration of fluid, and most importantlyblood, out of the main flow path within the pockets into stagnant areasadjacent the mouths of the pockets, thus greatly reducing thepossibility of substantial amounts of blood clotting taking place in theheat exchange device.

An added advantage of the device of this invention is that it operateswith a constant volume in its flow channels irrespective of moderatechanges in pressure in the flow channels. This is important in surgicaloperations, so that the amount of blood present in the heat exchangesystem can be readily determined without calculation.

In the drawings,

FIG. l is a plan view of the heat exchange device of this invention,showing one manifold thereof.

FIG. 2 is an elevational view of the heat exchange device of thisinvention, showing both manifolds and a portion of the convoluted heattransfer wall.

FIG. 3 is a vertical sectional view of FIG. 2 showing details of theconvoluted heat transfer wall and the general pattern of flow ofseparate fluids through the heat exchanger device.

FIG. 4 is a bottom plan view as indicated by line 4 4 of FIG. 3 of onemanifold used in the device of this invention, showing the internal sideof the manifold which presses against and secures convolutions of theheat transfer wall` FIG. 5 is a transverse section taken along line 5-5of FIGS. 2 and 3.

Referring to the drawings, a heat exchange device is shown in which apair of manifolds l0, l2 bracket and sealingly secure convolutions 14 ofa heat transfer wall 16. Manifolds l0, l2 can be molded from anelastomeric material, typically silicone rubber or anotherantithrombogenic material such as suitable formulations of polyurethaneor other thermoplastic or cross-linked elastomeric materials.

Each manifold l0, l2 comprises an inlet 18, 18a, and an outlet 20, 20a,as well as a plurality of continuous sealing ridges 22, 22a, to fit intothe mouths of oppositely opening pockets 24, 24a defined by convolutedheat transfer wall 16. Ridges 22, 22a provide anchoring to theindividual convolutions l4 of heat transfer wall 16, preventing theirlateral movement, with the resultant benefits described above. Theridges 22, 22a also are desirably proportioned and sufficientlyelastomeric to provide a generally fluidtight seal at the mouth of eachof pockets 24, 24a to prevent fluid, and particularly blood, frompassing out of the mouths of the pockets into stagnant areas 26, 26a, inwhich flow through the device is substantially reduced and bloodclotting may take place.

It is of course readily seen that one of the manifolds, the one whichdoes not seal the blood flow path, is not required to perform its pocketmouth sealing function with the same urgency as the manifold sealing theblood flow bath, but it is generally convenient to manufacture the twomanifolds out of the same material and in the same mold.

Each manifold has outer walls 28, 28a to grip the convolutions of theheat transfer wall for both fluidtight sealing and holding theconvolutions in position.

Referring to FIG. 3, a typical flow pattern of two separate fluids intwo oppositely facing pockets 24, 24a is shown. One fluid, typicallyblood, passes into the heat exchange device through fluid inlet 18 andis spread out by plenum 30 to permit blood to flow to every pocket 24 incommunication with plenum 30. Blood flow path 32 is shown in which theblood passes into each pocket 24, moves horizontally through the lengthof each pocket 24, being prevented from passing out of the mouths ofeach pocket by continuous sealing ridge 22, and then is collected inplenum 34 and passes out of fluid outlet 20.

In similar manner, a second fluid, typically a heat exchange fluid suchas saline solution, enters a second fluid inlet 18a, which communicateswith each of pockets 24a. Fluid flow path 36 is shown in dotted line,being behind convoluted heat transfer wall 16, with the exception ofwhere a portion of wall 16 is broken away to expose a portion of pocket24a to direct view. The heat transfer fluid flow path 36 runs in asimilar manner through the length of each pocket 24a, and exits throughfluid outlet 20a.

Each pocket 24 is in close contact with at least one and usually twopockets 24a. Thus, as the blood passes through pocket 24 and heatexchange fluid through pockets 24a, there is a heat transfer from onefluid to the other through the convoluted wall I6 without any mixing ofthe two fluids.

Generally, the heat transfer fluid is brought from a large fluid sourcein which the temperature is externally controlled as desired, and thetwo fluid flow rates controlled so that the blood has achieved thedesired temperature by the time it reaches fluid outlet 20.

The ends of convoluted heat transfer wall 16 are potted with sealant 35to prevent fluid leakage from the ends of pockets 24, 24a. Such sealantis typically an organosilicon room temperature vulcanizing elastomer ofatype which is readily commercially available. The areas between outerlateral walls 28, 28a of each manifold and convoluted heat transfer wall16 are also potted with linear beads 37 of sealant to prevent fluidleakage. However, a gap is left between sealant beads 37, exposing partof convoluted wall 16 to the exterior, to further reduce the possibilityof seepage of fluid from one flow path to the other.

To provide additional anchoring of the convolutions of wall 16, and alsoto accommodate the receiving and holding of sealant 3S, ridge extensions38 are provided for sealing fit into the ends of the mouths of pockets24, 24a. Ridge extensions 38 are beveled outwardly as shown in FIG. 3 toreceive the sealant. The ridge extensions and sealant 35 firmly seal theends of manifolds 10, l2 to the ends of wall 16, preventing anyundesirable lateral "play between them, and preventing accidentalremoval of the manifolds.

The flow of the two fluids through the heat exchanger device of thisinvention is shown to be countercurrent in nature, which is thepreferred technique, but it is contemplated that cocurrent flow can alsobe used, in which the two fluids flow in the same direction, if desired.

Each inlet 18, 18a and outlet 20, 20a has a flange 40 defined about itsend. This permits connection with another flanged tube in order toconnect the heat exchange device of this invention with organ perfusionequipment, a heat exchange fluid source, blood conduits, or any otherapparatus as desired. Flanges 40 permit the connection to anotherflanged tube by any connector device desired, such as the device definedin U.S. Pat. No` 3,456,965.

The face of convoluted wall 16 which is intended for contact with bloodis typically coated with a thin silicone resin or elastomer coating, torender wall 16 antithrombogenic.

The above disclosure is for illustrative purposes only, and not forpurposes of limitation, the invention of this application being definedin the claims below.

That which is claimed is:

l. A heat exchanger device which defines a heat transfer wall ofconvoluted shape to define a first set and a second set of flow channeldefining pockets, the mouth of the pockets of the first set opening in adirection opposite to the mouths of the pockets of the second set, afluid inlet and a fluid outlet disposed adjacent opposite ends of thepocket mouths of each of said first and second sets, and sets ofcontinuous sealing ridges fitting into said pocket mouths between eachsaid fluid inlet and outlet to provide flow channels of unvarying widthby preventing transverse movement of the convolutions of said heattransfer wall, and to seal said pocket mouths between each said fluidinlet and outlet.

2. The device of claim 1 in which said fluid inlet, fluid outlet, andset of continuous ridges communicating with a single set of pocketmouths are defined by a unitary, elastomeric manifold fitting over eachset of pockets.

3. The device of claim 2 in which the ends of said convoluted heattransfer wall are potted with sealant to prevent fluid leakage from theends of said pockets.

4. The device of claim 3 in which each said manifold has separate ridgeextensions at the ends thereof for sealing fit into said pockets, saidridge extensions being beveled outwardly to receive said sealant.

5. The device of claim 4 in which the outer lateral walls of saidmanifolds are sealed to said convoluted heat transfer wall with beads ofsealant which are spaced from each other to expose portions of said heattransfer wall between said sealant beads to the exterior.

1. A heat exchanger device which defines a heat transfer wall ofconvoluted shape to define a first set and a second set of flow channeldefining pockets, the mouths of the pockets of the first set opening ina direction opposite to the mouths of the pockets of the seCond set, afluid inlet and a fluid outlet disposed adjacent opposite ends of thepocket mouths of each of said first and second sets, and sets ofcontinuous sealing ridges fitting into said pocket mouths between eachsaid fluid inlet and outlet to provide flow channels of unvarying widthby preventing transverse movement of the convolutions of said heattransfer wall, and to seal said pocket mouths between each said fluidinlet and outlet.
 2. The device of claim 1 in which each fluid inlet,fluid outlet, and set of continuous ridges communicating with a singleset of pocket mouths are defined by a unitary, elastomeric manifoldfitting over each set of pockets.
 3. The device of claim 2 in which theends of said convoluted heat transfer wall are potted with sealant toprevent fluid leakage from the ends of said pockets.
 4. The device ofclaim 3 in which each said manifold has separate ridge extensions at theends thereof for sealing fit into said pockets, said ridge extensionsbeing beveled outwardly to receive said sealant.
 5. The device of claim4 in which the outer lateral walls of said manifolds are sealed to saidconvoluted heat transfer wall with beads of sealant which are spacedfrom each other to expose portions of said heat transfer wall betweensaid sealant beads to the exterior.